This invention relates generally to xerographic copying apparatus and, more particularly, to a contact fusing system and cleaning mechanism therefor for fixing electroscopic toner material to a support member.
In the process of xerography, a light image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a photosensitive member with subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual image can be either fixed directly upon the photosensitive member or transferred from the member to a sheet of plain paper with subsequent affixing of the image thereto.
In order to permanently affix or fuse electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the support member which, in many instances, constitutes plain paper. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be firmly bonded to the support member. In both the xerographic as well as the electrographic recording arts, the use of thermal energy for fixing toner images onto a support member is old and well known.
One approach to thermal fusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed roller members, at least one of which is internally heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the heated roll to thereby effect heating of the toner images within the nip. By controlling the heat transferred to the toner, virtually no offset of the toner particles from the copy sheet to the fuser roll is experienced under normal conditions. This is because the heat applied to the surface of the roller is insufficient to raise the temperature of the surface of the roller above the "hot offset" temperature of the toner whereat the toner particles in the image areas of the toner would liquify and cause a splitting action in the molten toner to thereby result in hot offset. Splitting occurs when the cohesive forces holding the viscous toner mass together are less than the adhesive forces tending to offset it to a contacting surface such as a fuser roll.
However, toner particles will be offset to the fuser roll by an insufficient application of heat to the surface thereof (i.e. "cold" offsetting); by imperfections in the properties of the surface of the roll; or by the toner particles insufficiently adhering to the copy sheet by the electrostatic forces which normally hold them there. In such a case, toner particles may be transferred to the surface of the fuser roll with subsequent transfer to the backup roll during periods of time when no copy paper is in the nip.
Moreover, toner particles can be picked up by the fuser and/or backup roll during fusing of duplex copies or simply from the surroundings of the reproducing apparatus.
Various arrangements for minimizing the problems attendant the foregoing, particularly that which is commonly referred to as "offsetting" are known in the art. Notwithstanding such arrangements, it is still necessary to provide means for cleaning toner and other contaminants from the roll members, particularly, the fuser roll.
One means of cleaning toner and other contaminants from a fuser roll structure is by the provision of a cleaning member having a surface which is tacky at the operating temperature of the fuser roll. Such tackiness is usually provided by having a coating of polymer material comprising the outer layer or coating of the cleaning member. While such a cleaning member has been found to be acceptable it has also been discovered that during certain modes of operation of the copying apparatus the cleaning efficiency of such a member can be adversely affected.
Accordingly, the primary object of this invention is to provide a new and improved contact fuser system for fixing toner images to substrates.
A more particular object of this invention is to provide, in a contact fuser system, means for cleaning the heated fuser member from the contact fuser assembly .
Another object of this invention is to provide, in a contact fusing apparatus, structure for cleaning contaminants from a heated member of the fusing apparatus wherein the cleaning structure has a tacky surface in which the contaminants become embedded.
Still another object of this invention is to provide, in a fuser apparatus, apparatus and a method for cleaning a heated fuser member wherein the cleaning member is provided with a tacky surface capable of having contaminants removed from the fuser member embedded therein and wherein a mixing member is provided for increasing the toner embedding rate or efficiency of the tacky surface.